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1.  Demasculinization and feminization of male gonads by atrazine: Consistent effects across vertebrate classes 
Atrazine is the most commonly detected pesticide contaminant of ground water, surface water, and precipitation. Atrazine is also an endocrine disruptor that, among other effects, alters male reproductive tissues when animals are exposed during development. Here, we apply the nine so-called “Hill criteria” (Strength, Consistency, Specificity, Temporality, Biological Gradient, Plausibility, Coherence, Experiment, and Analogy) for establishing cause–effect relationships to examine the evidence for atrazine as an endocrine disruptor that demasculinizes and feminizes the gonads of male vertebrates. We present experimental evidence that the effects of atrazine on male development are consistent across all vertebrate classes examined and we present a state of the art summary of the mechanisms by which atrazine acts as an endocrine disruptor to produce these effects.
Atrazine demasculinizes male gonads producing testicular lesions associated with reduced germ cell numbers in teleost fish, amphibians, reptiles, and mammals, and induces partial and/or complete feminization in fish, amphibians, and reptiles. These effects are strong (statistically significant), consistent across vertebrate classes, and specific. Reductions in androgen levels and the induction of estrogen synthesis – demonstrated in fish, amphibians, reptiles, and mammals – represent plausible and coherent mechanisms that explain these effects. Biological gradients are observed in several of the cited studies, although threshold doses and patterns vary among species. Given that the effects on the male gonads described in all of these experimental studies occurred only after atrazine exposure, temporality is also met here. Thus the case for atrazine as an endocrine disruptor that demasculinizes and feminizes male vertebrates meets all nine of the “Hill criteria”.
PMCID: PMC4303243  PMID: 21419222
Atrazine; Gonads; Endocrine disruptor
2.  Synergistic Signaling of KRAS and Thyroid Hormone Receptor β Mutants Promotes Undifferentiated Thyroid Cancer through MYC Up-Regulation12 
Neoplasia (New York, N.Y.)  2014;16(9):757-769.
Undifferentiated thyroid carcinoma is one of the most aggressive human cancers with frequent RAS mutations. How mutations of the RAS gene contribute to undifferentiated thyroid cancer remains largely unknown. Mice harboring a potent dominant negative mutant thyroid hormone receptor β, TRβPV (ThrbPV/PV), spontaneously develop well-differentiated follicular thyroid cancer similar to human cancer. We genetically targeted the KrasG12D mutation to thyroid epithelial cells of ThrbPV/PV mice to understand how KrasG12D mutation could induce undifferentiated thyroid cancer in ThrbPV/PVKrasG12D mice. ThrbPV/PVKrasG12D mice exhibited poorer survival due to more aggressive thyroid tumors with capsular invasion, vascular invasion, and distant metastases to the lung occurring at an earlier age and at a higher frequency than ThrbPV/PV mice did. Importantly, ThrbPV/PVKrasG12D mice developed frequent anaplastic foci with complete loss of normal thyroid follicular morphology. Within the anaplastic foci, the thyroid-specific transcription factor paired box gene 8 (PAX8) expression was virtually lost and the loss of PAX8 expression was inversely correlated with elevated MYC expression. Consistently, co-expression of KRASG12D with TRβPV upregulated MYC levels in rat thyroid pccl3 cells, and MYC acted to enhance the TRβPV-mediated repression of the Pax8 promoter activity of a distant upstream enhancer, critical for thyroid-specific Pax8 expression. Our findings indicated that synergistic signaling of KRASG12D and TRβPV led to increased MYC expression. Upregulated MYC contributes to the initiation of undifferentiated thyroid cancer, in part, through enhancing TRβPV-mediated repression of the Pax8 expression. Thus, MYC might serve as a potential target for therapeutic intervention.
PMCID: PMC4234871  PMID: 25246276
3.  Isolation and mutational analysis of circulating tumor cells from lung cancer patients with magnetic sifters and biochips† 
Lab on a chip  2014;14(1):78-88.
Detection and characterization of circulating tumor cells (CTCs) may reveal insights into the diagnosis and treatment of malignant disease. Technologies for isolating CTCs developed thus far suffer from one or more limitations, such as low throughput, inability to release captured cells, and reliance on expensive instrumentation for enrichment or subsequent characterization. We report a continuing development of a magnetic separation device, the magnetic sifter, which is a miniature microfluidic chip with a dense array of magnetic pores. It offers high efficiency capture of tumor cells, labeled with magnetic nanoparticles, from whole blood with high throughput and efficient release of captured cells. For subsequent characterization of CTCs, an assay, using a protein chip with giant magnetoresistive nanosensors, has been implemented for mutational analysis of CTCs enriched with the magnetic sifter. The use of these magnetic technologies, which are separate devices, may lead the way to routine preparation and characterization of “liquid biopsies” from cancer patients.
PMCID: PMC4144998  PMID: 23969419
4.  Calreticulin is the dominant pro-phagocytic signal on multiple human cancers and is counterbalanced by CD47 
Science translational medicine  2010;2(63):63ra94.
Under normal physiologic conditions, cellular homeostasis is partly regulated by balancing pro- and anti-phagocytic signals. CD47 is highly expressed on several human cancers including acute myeloid leukemia, non-Hodgkin lymphoma, and bladder cancer, allowing cancer cells to evade phagocytosis by the innate immune system. Blockade of CD47 with a monoclonal antibody enables phagocytosis of cancer cells and leads to in vivo tumor elimination, but leaves most normal cells unaffected. In order for target cells to be phagocytosed upon blockade of an anti-phagocytic signal, we postulate that the cells must also display a potent pro-phagocytic signal. Here we identify calreticulin as a pro-phagocytic signal highly expressed on the surface of several human cancers including acute myeloid and lymphoblastic leukemias, chronic myeloid leukemia, non-Hodgkin lymphoma (NHL), bladder cancer, glioblastoma, and ovarian cancer, but minimally expressed on most normal cells. Increased CD47 expression correlated with high calreticulin levels on cancer cells, and was necessary for protection from calreticulin-mediated phagocytosis. Phagocytosis induced by anti-CD47 antibody required the interaction of target cell calreticulin with its receptor low density lipoprotein-receptor related protein (LRP) on phagocytic cells, as blockade of the calreticulin/LRP interaction prevented anti-CD47 antibody mediated phagocytosis. Lastly, increased calreticulin expression was an adverse prognostic factor in diverse tumors including neuroblastoma, bladder cancer, and NHL. These findings identify calreticulin as the dominant pro-phagocytic signal on several human cancers, provide an explanation for the selective targeting of tumor cells by anti-CD47 antibody, and highlight the balance between pro- and anti-phagocytic signals in the immune evasion of cancer.
PMCID: PMC4126904  PMID: 21178137
5.  Molecular Detection of Leptospiral DNA in Environmental Water on St. Kitts 
Leptospirosis is an important waterborne zoonotic disease caused by pathogenic Leptospira. The pathogen is maintained in a population due to chronic colonization and shedding from renal tubules of domestic and wild animals. Humans and other animals become infected when they come in contact with urine from infected animals, either directly or through urine-contaminated surface water. In this study, we screened environmental water on the island of St. Kitts by using a TaqMan based real time quantitative polymerase chain reaction (qPCR) targeting a pathogen specific leptospiral gene, lipl32. Our results indicate that around one-fifth of tested water sources have detectable leptospiral DNA.
PMCID: PMC4143842  PMID: 25105546
Leptospira; molecular detection; environmental transmission; leptospirosis
6.  Increased Incidence of Benign Pancreatic Pathology following Pancreaticoduodenectomy for Presumed Malignancy over 10 Years despite Increased Use of Endoscopic Ultrasound 
Despite using imaging studies, tissue sampling, and serologic tests about 5–10% of surgeries done for presumed pancreatic malignancies will have benign findings on final pathology. Endoscopic ultrasound (EUS) is used with increasing frequency to study pancreatic masses. The aim of this study is to examine the effect of EUS on prevalence of benign diseases undergoing Whipple over the last decade. Patients who underwent Whipple procedure for presumed malignancy at Emory University Hospital from 1998 to 2011 were selected. Demographic data, history of smoking and drinking, history of diabetes and pancreatitis, imaging data, pathology reports, and tumor markers were extracted. 878 patients were found. 95 (10.82%) patients had benign disease. Prevalence of benign finding had increased over the recent years despite using more EUS. Logistic regression models showed that abdominal pain (OR: 5.829, 95% CI 2.681–12.674, P ≤ 0.001) and alcohol abuse (OR: 3.221, CI 95%: 1.362–7.261, P: 0.002) were predictors of benign diseases. Jaundice (OR: 0.221, 95% CI: 0.084–0.58, P: 0.002), mass (OR: 0.145, 95% CI: 0.043–0.485, P: 0.008), and ductal dilation (OR: 0.297, 95% CI 0.134–0.657, P: 0.003) were associated with malignancy. Use of imaging studies, ERCP, and EUS has not decreased the percentage of benign findings after surgery for presumed pancreatic malignancy.
PMCID: PMC4068051  PMID: 25002810
7.  Variation in Susceptibility of Human Malignant Melanomas to Oncolytic Vesicular Stomatitis Virus 
Surgery  2012;153(3):333-343.
Vesicular stomatitis virus (VSV) is a novel, anti-cancer therapy that selectively targets cancer cells with defective antiviral responses; however, not all malignant cells are sensitive to the oncolytic effects of VSV. Herein, we explore the mechanistic determinants of mutant M protein VSV (M51R-VSV) susceptibility in malignant melanoma cells.
Cell viability after VSV infection was measured by the 3-(4,5-dimethylthiazol-2-yl)-5-(3-carboxymethoxyphenyl)-2-(4-sulfophenyl)-2H-tetrazolium (MTS) viability assay in a panel of melanoma cell lines. VSV infectability, viral protein synthesis and viral progeny production were quantified by flow cytometry, 35S-methionine electrophoresis, and viral plaque assays, respectively. Interferon (IFN) responsiveness was determined using MTS assay after β-IFN pre-treatment. Xenografts were established in athymic nude mice and treated with intratumoral M51R-VSV.
Cell viability after M51R-VSV infection at a multiplicity of infection (MOI) of 10 pfu/mL, 48 hours post-infection) ranged between 0±1 and 59±9% (mean ± standard deviation). Sensitive cell lines supported VSV infection, viral protein synthesis, and viral progeny production. In addition, when pre-treated with β-IFN, sensitive cells became resistant to M51R-VSV, suggesting that IFN-mediated antiviral signaling is defective in these cells. In contrast, resistant melanoma cells do not support VSV infection, viral protein synthesis, or viral replication, indicating that anti-viral defenses remain intact. In a murine xenograft model, intratumoral M51R-VSV treatment decreased tumor growth relative to controls after 26 days in SK-Mel 5 (−21±19% vs. 2100±770%, p<0.0001) and SK-Mel 3 (2000±810% vs 7000±3000%, p=0.008) established tumors.
M51R-VSV is a viable, anti-cancer therapy, but susceptibility varies among melanomas. Future work will exploit specific mechanisms of resistance to expand the therapeutic efficacy of M51R-VSV.
PMCID: PMC3561511  PMID: 23102637
8.  Learning from Host-Defense Peptides: Cationic, Amphipathic Peptoids with Potent Anticancer Activity 
PLoS ONE  2014;9(2):e90397.
Cationic, amphipathic host defense peptides represent a promising group of agents to be developed for anticancer applications. Poly-N-substituted glycines, or peptoids, are a class of biostable, peptidomimetic scaffold that can display a great diversity of side chains in highly tunable sequences via facile solid-phase synthesis. Herein, we present a library of anti-proliferative peptoids that mimics the cationic, amphipathic structural feature of the host defense peptides and explore the relationships between the structure, anticancer activity and selectivity of these peptoids. Several peptoids are found to be potent against a broad range of cancer cell lines at low-micromolar concentrations including cancer cells with multidrug resistance (MDR), causing cytotoxicity in a concentration-dependent manner. They can penetrate into cells, but their cytotoxicity primarily involves plasma membrane perturbations. Furthermore, peptoid 1, the most potent peptoid synthesized, significantly inhibited tumor growth in a human breast cancer xenotransplantation model without any noticeable acute adverse effects in mice. Taken together, our work provided important structural information for designing host defense peptides or their mimics for anticancer applications. Several cationic, amphipathic peptoids are very attractive for further development due to their high solubility, stability against protease degradation, their broad, potent cytotoxicity against cancer cells and their ability to overcome multidrug resistance.
PMCID: PMC3938723  PMID: 24587350
9.  A Low Gastric pH Mouse Model to Evaluate Live Attenuated Bacterial Vaccines 
PLoS ONE  2014;9(1):e87411.
The low pH of the stomach serves as a barrier to ingested microbes and must be overcome or bypassed when delivering live bacteria for vaccine or probiotic applications. Typically, the impact of stomach acidity on bacterial survival is evaluated in vitro, as there are no small animal models to evaluate these effects in vivo. To better understand the effect of this low pH barrier to live attenuated Salmonella vaccines, which are often very sensitive to low pH, we investigated the value of the histamine mouse model for this application. A low pH gastric compartment was transiently induced in mice by the injection of histamine. This resulted in a gastric compartment of approximately pH 1.5 that was capable of distinguishing between acid-sensitive and acid-resistant microbes. Survival of enteric microbes during gastric transit in this model directly correlated with their in vitro acid resistance. Because many Salmonella enterica serotype Typhi vaccine strains are sensitive to acid, we have been investigating systems to enhance the acid resistance of these bacteria. Using the histamine mouse model, we demonstrate that the in vivo survival of S. Typhi vaccine strains increased approximately 10-fold when they carried a sugar-inducible arginine decarboxylase system. We conclude that this model will be a useful for evaluating live bacterial preparations prior to clinical trials.
PMCID: PMC3906194  PMID: 24489912
10.  Low-pH Rescue of Acid-Sensitive Salmonella enterica Serovar Typhi Strains by a Rhamnose-Regulated Arginine Decarboxylase System 
Journal of Bacteriology  2013;195(13):3062-3072.
For Salmonella, transient exposure to gastric pH prepares invading bacteria for the stresses of host-cell interactions. To resist the effects of low pH, wild-type Salmonella enterica uses the acid tolerance response and the arginine decarboxylase acid resistance system. However, arginine decarboxylase is typically repressed under routine culture conditions, and for many live attenuated Salmonella vaccine strains, the acid tolerance response is unable to provide the necessary protection. The objective of this study was to enhance survival of Salmonella enterica serovar Typhi vaccine strains at pHs 3.0 and 2.5 to compensate for the defects in the acid tolerance response imposed by mutations in rpoS, phoPQ, and fur. We placed the arginine decarboxylase system (adiA and adiC) under the control of the ParaBAD or PrhaBAD promoter to provide inducible acid resistance when cells are grown under routine culture conditions. The rhamnose-regulated promoter PrhaBAD was less sensitive to the presence of its cognate sugar than the arabinose-regulated promoter ParaBAD and provided tighter control over adiA expression. Increased survival at low pH was only observed when adiA and adiC were coregulated by rhamnose and depended on the presence of rhamnose in the culture medium and arginine in the challenge medium. Rhamnose-regulated acid resistance significantly improved the survival of ΔaroD and ΔphoPQ mutants at pHs 3 and 2.5 but only modestly improved the survival of a fur mutant. The construction of the rhamnose-regulated arginine decarboxylase system allowed us to render S. Typhi acid resistant (to pH 2.5) on demand, with survival levels approximately equivalent to that of the native arginine decarboxylase system.
PMCID: PMC3697538  PMID: 23645603
11.  Angiotensin-(1-7) Attenuates Metastatic Prostate Cancer and Reduces Osteoclastogenesis 
The Prostate  2012;73(1):10.1002/pros.22542.
Angiotensin-(1-7) [Ang-(1-7)] is an endogenous, heptapeptide hormone with anti-proliferative and anti-angiogenic properties. The primary objective of this study was to determine whether Ang-(1-7) effectively reduces prostate cancer metastasis in mouse xenografts.
Human PC3 prostate cancer cells were injected into the aortic arch via the carotid artery of SCID mice pretreated with Ang-(1-7) or injected into the tibia of athymic mice, administered Ang-(1-7) for 5 weeks beginning 2 weeks post-injection. Tumor growth and volume were determined by bioluminescent and magnetic resonance imaging. The presence of tumors was confirmed by hematoxylin and eosin staining; TRAP histochemistry was used to identify osteolytic lesions. The effect of Ang-(1-7) on osteoclastogenesis was assessed in differentiated bone marrow cells.
Pre-treatment with Ang-(1-7) prevented metastatic tumor formation following intra-aortic injection of PC3 cells, while 83% of untreated mice developed tumors in metastatic sites. Circulating VEGF was significantly higher in control mice compared to mice administered Ang-(1-7). A five-week regimen of the heptapeptide hormone attenuated intra-tibial tumor growth; Ang-(1-7) was significantly higher in the tibia of treated mice than in control animals. Osteoclastogenesis was reduced by 50% in bone marrow cells differentiated in the presence of Ang-(1-7), suggesting that the heptapeptide hormone prevents the formation of osteolytic lesions to reduce tumor survival in the bone microenvironment.
These findings suggest that Ang-(1-7) may serve as an anti-angiogenic and anti-metastatic agent for advanced prostate cancer. By extension, the heptapeptide hormone may provide effective therapy for bone metastasis produced from primary tumors of the lung and breast.
PMCID: PMC3842188  PMID: 22644942
angiotensin-(1-7); metastatic prostate cancer; vascular endothelial growth factor; osteoclasts
12.  Temperature effects in the sputtering of a molecular solid by energetic atomic and cluster projectiles 
Surface and interface analysis : SIA  2011;43(1-2):10.1002/sia.3505.
Temperature effects in the sputtering of an organic molecule were investigated by subjecting a well defined film of coronene to Au1 and C60 primary ions at 100 and 300 K. Strong field photoionization of the sputtered neutral flux was employed to monitor the change in flight time and kinetic energy distributions of intact and fragmented species.
PMCID: PMC3863433  PMID: 24347745
temperature effects; photoionization; C60 sputtering; molecular solid; organic film
13.  Cannulation time is a more accurate measure of cannulation difficulty in endoscopic retrograde cholangiopancreatography than the number of attempts 
Gastroenterology Report  2013;1(3):193-197.
Background: Cannulation of the common bile duct (CBD) is the initial and sometime challenging step in endoscopic retrograde cholangiopancreatography (ERCP) procedure. Endoscopists often use cannulation attempts and cannulation time to grade cannulation difficulty, but a standard system has yet to be established. The objective of this study was to compare cannulation times with numbers of cannulation attempts, as measures of cannulation difficulty.
Methods: We conducted a prospective study in a tertiary referral center, enrolling 58 patients who were undergoing ERCP for a variety of indications. Cannulation time and the number of cannulation attempts were recorded for each patient. A subset of 14 ERCPs had two observers assessing attempts at cannulation. Cannulation time, number of attempts and inter-observer variability in assessment of attempts were compared and studied.
Results: The degree of agreement between two the methods (cannulation times and number of cannulation attempts) was unacceptable. There were considerable discrepancies between attempt tallies from two observers but the mean difference was statistically insignificant.
Conclusion: The grade of cannulation difficulty for a given ERCP procedure may differ when different methods are used (total cannulation time vs number of attempts); thus, grading by different methods should not be used interchangeably. Cannulation time is a more objective and more accurate assessment tool for grading cannulation difficulty than the number of attempts to cannulate the papilla.
PMCID: PMC3938000  PMID: 24759965
endoscopic retrograde cholangiopancreatography; cannulation attempts; cannulation times
14.  Prognostic value of the hDMP1-ARF-Hdm2-p53 pathway in breast cancer 
Oncogene  2012;32(35):4120-4129.
Our recent study showed critical roles of Dmp1 as a sensor of oncogenic Ras, HER2/neu signaling and activation of the Arf-p53 pathway. To elucidate the role of human DMP1 (hDMP1) in breast cancer, one hundred and ten pairs of human breast cancer specimen were studied for the alterations of the hDMP1-ARF-Hdm2-p53 pathway with follow up of clinical outcomes. Loss of heterozygosity (LOH) of the hDMP1 locus was found in 42% of human breast carcinomas, while that of INK4a/ARF and p53 were found in 20% and 34%, respectively. Hdm2 amplification was found in 13% of the same sample, which was found independently of LOH for hDMP1. Conversely, LOH for hDMP1 was found in mutually exclusive fashion with that of INK4a/ARF and p53, and was associated with low Ki67 index and diploid karyotype. Consistently, LOH for hDMP1 was associated with luminal A category and longer relapse-free survival, while that of p53 was associated with non-luminal A and shorter survival. Thus, loss of hDMP1 could define a new disease category associated with prognosis of breast cancer patients. Human breast epithelial cells/cancer cells with wild-type p53 were sensitive to growth inhibition by activated Dmp1:ER while those that delete p14ARF or p53, and/or Hdm2 amplification showed partial or nearly complete resistance, indicating that p53 is a critical target for hDMP1 to exhibit its biological activity.
PMCID: PMC3742602  PMID: 23045280
Dmp1 (Dmtf1); breast cancer; loss of heterozygosity; relapse-free survival; Ki67; prognostic marker
15.  Role of DMP1 and its future in lung cancer diagnostics 
Lung cancer is the most lethal carcinoma worldwide. Mutations of p53, inactivation of p16INK4a, and overexpression of cyclins E, A and B are independently associated with poor prognoses of patients, while the prognostic value of cyclin D1 or RB expression is inconclusive. Cyclin D binding myb-like protein 1 (Dmp1) encodes a DNA binding protein that receives signals from oncogenic Ras and functions as a tumor suppressor by activating the Arf-p53 pathway. Dmp1 has been shown to be haplo-insufficient for tumor suppression in mouse models including K-ras-mediated lung carcinogenesis. The human DMP1 gene is located on chromosome 7q21, and our recent results revealed that the hDMP1 gene is deleted, but not mutated or silenced, in approximately 40 % of human non-small-cell lung carcinomas. These cases typically retained wild-type ARF and p53 and expressed very low levels of the hDMP1 protein. Thus, hDMP1 loss could be a novel diagnostic marker for non-small-cell lung carcinomas.
PMCID: PMC3749846  PMID: 18598225
ARF; DMP1l; haploid insufficiency; immunohistochemistryl; LOHl; loss of heterozygosity; lung cancer; p16INK4a; p53; Ras; tumor-suppressor gene
16.  MYRF Is a Membrane-Associated Transcription Factor That Autoproteolytically Cleaves to Directly Activate Myelin Genes 
PLoS Biology  2013;11(8):e1001625.
Oligodendrocyte development and myelination rely on an unusual membrane-associated transcription factor that shares functional domains with bacteriophage proteins.
The myelination of axons is a crucial step during vertebrate central nervous system (CNS) development, allowing for rapid and energy efficient saltatory conduction of nerve impulses. Accordingly, the differentiation of oligodendrocytes, the myelinating cells of the CNS, and their expression of myelin genes are under tight transcriptional control. We previously identified a putative transcription factor, Myelin Regulatory Factor (Myrf), as being vital for CNS myelination. Myrf is required for the generation of CNS myelination during development and also for its maintenance in the adult. It has been controversial, however, whether Myrf directly regulates transcription, with reports of a transmembrane domain and lack of nuclear localization. Here we show that Myrf is a membrane-associated transcription factor that undergoes an activating proteolytic cleavage to separate its transmembrane domain-containing C-terminal region from a nuclear-targeted N-terminal region. Unexpectedly, this cleavage event occurs via a protein domain related to the autoproteolytic intramolecular chaperone domain of the bacteriophage tail spike proteins, the first time this domain has been found to play a role in eukaryotic proteins. Using ChIP-Seq we show that the N-terminal cleavage product directly binds the enhancer regions of oligodendrocyte-specific and myelin genes. This binding occurs via a defined DNA-binding consensus sequence and strongly promotes the expression of target genes. These findings identify Myrf as a novel example of a membrane-associated transcription factor and provide a direct molecular mechanism for its regulation of oligodendrocyte differentiation and CNS myelination.
Author Summary
Oligodendrocytes are a highly specialized cell type that surround axons of the vertebrate central nervous system with myelin, electrically insulating them and allowing rapid and energy-efficient propagation of nerve signals. We previously identified a protein, MYRF, that is required for the final stages of oligodendrocyte differentiation and myelination. Although we proposed that MYRF might act as a transcription factor, it remains uncertain whether this is true, given that MYRF and related proteins contain a transmembrane domain that might preclude localization to the nucleus. Here, we show that the MYRF protein undergoes an activating cleavage event to release the functional transcription factor from the transmembrane domain that otherwise anchors it to the endoplasmic reticulum. Unexpectedly, this cleavage event is mediated by a portion of MYRF that is related to a self-cleaving domain found in bacteriophage proteins. This distinguishes it from other membrane-associated transcription factors that are cleaved via regulated proteolysis within the membrane bilayer. We find that the N-terminal product of MYRF cleavage directly binds to a wide range of genes involved in myelination, stimulating their expression. Many of these MYRF binding sites identify previously uncharacterized enhancers for these myelin genes.
PMCID: PMC3742440  PMID: 23966833
17.  Ferroportin and Iron Regulation in Breast Cancer Progression and Prognosis 
Science translational medicine  2010;2(43):43ra56.
Ferroportin and hepcidin are critical proteins for the regulation of systemic iron homeostasis. Ferroportin is the only known mechanism for export of intracellular non–heme-associated iron; its stability is regulated by the hormone hepcidin. Although ferroportin profoundly affects concentrations of intracellular iron in tissues important for systemic iron absorption and trafficking, ferroportin concentrations in breast cancer and their influence on growth and prognosis have not been examined. We demonstrate here that both ferroportin and hepcidin are expressed in cultured human breast epithelial cells and that hepcidin regulates ferroportin in these cells. Further, ferroportin protein is substantially reduced in breast cancer cells compared to nonmalignant breast epithelial cells; ferroportin protein abundance correlates with metabolically available iron. Ferroportin protein is also present in normal human mammary tissue and markedly decreased in breast cancer tissue, with the highest degree of anaplasia associated with lowest ferroportin expression. Transfection of breast cancer cells with ferroportin significantly reduces their growth after orthotopic implantation in the mouse mammary fat pad. Gene expression profiles in breast cancers from >800 women reveal that decreased ferroportin gene expression is associated with a significant reduction in metastasis-free and disease-specific survival that is independent of other breast cancer risk factors. High ferroportin and low hepcidin gene expression identifies an extremely favorable cohort of breast cancer patients who have a 10-year survival of >90%. Ferroportin is a pivotal protein in breast biology and a strong and independent predictor of prognosis in breast cancer.
PMCID: PMC3734848  PMID: 20686179
18.  Activation of tumor cell proliferation by thyroid hormone in a mouse model of follicular thyroid carcinoma 
Oncogene  2011;31(16):2007-2016.
Thyroid cancers are the most common malignancy of the endocrine system in humans. To understand the molecular genetic events underlying thyroid carcinogenesis, we have generated a mouse model that spontaneously develops follicular thyroid carcinoma similar to human thyroid cancer (ThrbPV/PV mouse). This mutant mouse harbors a dominantnegative mutated thyroid hormone receptor β (denoted PV). The PV mutation was identified in a patient with resistance to thyroid hormone (TH). ThrbPV/PV mice exhibit highly elevated serum thyroid-stimulating hormone levels and increased TH. We have previously shown that thyroidstimulating hormone is required, but not sufficient to induce metastatic follicular thyroid cancer in ThrbPV/PV mice. However, whether the elevated TH also contributes to the thyroid carcinogenesis of ThrbPV/PV mice was not elucidated. To understand the role of TH in thyroid carcinogenesis, we blocked the production of TH by treating ThrbPV/PV mice with propylthiouracil (ThrbPV/PV-PTU mice) and compared the development of thyroid cancer in ThrbPV/PV-PTU and untreated ThrbPV/PV mice. We found that thyroid tumor growth was reduced by ~42% in ThrbPV/PV-PTU mice as compared with ThrbPV/PV mice. Analysis by bromodeoxyuridine- nuclear labeling showed decreased incorporation of bromodeoxyuridine in thyroid tumor cells of ThrbPV/PV-PTU mice, indicative of decreased tumor cell proliferation. However, cleaved-caspase 3 staining showed no apparent changes in apoptosis of tumor cells in ThrbPV/PV-PTU mice. Molecular studies identified a marked attenuation of the PI3K–AKT–β-catenin signaling pathway that led to decreased protein levels of cyclin D2, thereby decreasing tumor cell proliferation in ThrbPV/PV-PTU mice. Furthermore, matrix metalloproteinase-2, a downstream target of β-catenin and a key regulator during tumor invasion and metastasis, was also decreased. Thus, the present study uncovers a critical role of TH in promoting the thyroid carcinogenesis of ThrbPV/PV mice via membrane signaling events. Importantly, these findings suggest that anti-thyroid drugs could be considered as possible therapeutic agents of thyroid cancer.
PMCID: PMC3728834  PMID: 21909131
thyroid hormone; follicular thyroid carcinoma; animal model; protein kinase B/AKT; PTEN
19.  Polymorphisms in Drug Metabolism Genes, Smoking, and p53 Mutations in Breast Cancer 
Molecular carcinogenesis  2008;47(2):88-99.
Polymorphisms in phase I and phase II enzymes may enhance the occurrence of mutations at critical tumor suppressor genes, such as p53, and increase breast cancer risk by either increasing the activation or detoxification of carcinogens and/or endogenous estrogens. We analyzed polymorphisms in CYP1B1, GSTM1, GSTT1, and GSTP1 and p53 mutations in 323 breast tumor samples. Approximately 11% of patients exhibited mutations in p53. Women with mutations had a significantly younger age of diagnosis (P = 0.01) and a greater incidence of tumors classified as stage II or higher (P = 0.002). More women with mutations had a history of smoking (55%) compared to women without mutations (39%). Although none of the genotypes alone were associated with p53 mutations, positive smoking history was associated with p53 mutations in women with the GSTM1 null allele [OR = 3.54; 95% CI = 0.97–12.90 P = 0.06] compared to women with the wild-type genotype and smoking history [OR = 0.62, 95% CI = 0.19–2.07], although this association did not reach statistical significance. To test for gene–gene interactions, our exploratory analysis in the Caucasian cases suggested that individuals with the combined GSTP1 105 VV, CYP1B1 432 LV/VV, and GSTM1 positive genotype were more likely to harbor mutations in p53 [OR = 4.94; 95% CI = 1.11–22.06]. Our results suggest that gene–smoking and gene–gene interactions may impact the prevalence of p53 mutations in breast tumors. Elucidating the etiology of breast cancer as a consequence of common genetic polymorphisms and the genotoxic effects of smoking will enable us to improve the design of prevention strategies, such as lifestyle modifications, in genetically susceptible subpopulations.
PMCID: PMC3722359  PMID: 17683074
breast cancer; p53; polymorphisms; drug metabolism
20.  Oncogenic Actions of the Nuclear Receptor Corepressor (NCOR1) in a Mouse Model of Thyroid Cancer 
PLoS ONE  2013;8(6):e67954.
Studies have suggested that the nuclear receptor corepressor 1 (NCOR1) could play an important role in human cancers. However, the detailed molecular mechanisms by which it functions in vivo to affect cancer progression are not clear. The present study elucidated the in vivo actions of NCOR1 in carcinogenesis using a mouse model (ThrbPV/PV mice) that spontaneously develops thyroid cancer. ThrbPV/PV mice harbor a dominantly negative thyroid hormone receptor β (TRβ) mutant (denoted as PV). We adopted the loss-of-the function approach by crossing ThrbPV mice with mice that globally express an NCOR1 mutant protein (NCOR1ΔID) in which the receptor interaction domains have been modified so that it cannot interact with the TRβ, or PV, in mice. Remarkably, expression of NCOR1ΔID protein reduced thyroid tumor growth, markedly delayed tumor progression, and prolonged survival of ThrbPV/PVNcor1ΔID/ΔID mice. Tumor cell proliferation was inhibited by increased expression of cyclin-dependent kinase inhibitor 1 (p21waf1/cip1; Cdkn1A), and apoptosis was activated by elevated expression of pro-apoptotic BCL-Associated X (Bax). Further analyses showed that p53 was recruited to the p53-binding site on the proximal promoter of the Cdkn1A and the Bax gene as a co-repressor complex with PV/NCOR1/histone deacetylas-3 (HDAC-3), leading to repression of the Cdkn1A as well as the Bax gene in thyroids of ThrbPV/PV mice. In thyroids of ThrbPV/PVNcor1ΔID/ΔID mice, the p53/PV complex could not recruit NCOR1ΔID and HDAC-3, leading to de-repression of both genes to inhibit cancer progression. The present studies provided direct evidence in vivo that NCOR1 could function as an oncogene via transcription regulation in a mouse model of thyroid cancer.
PMCID: PMC3694063  PMID: 23840792
21.  Vesicular stomatitis virus as a treatment for colorectal cancer 
Cancer gene therapy  2011;18(12):837-849.
M protein mutant vesicular stomatitis virus is an attractive candidate oncolytic virus for the treatment of metastatic colorectal cancer due to its ability to kill cancer cells that are defective in their antiviral responses. The oncolytic activity of recombinant wild-type and M protein mutant vesicular stomatitis viruses was determined in RKO, Hct116 and LoVo colorectal cancer cells, as well as in human fibroblast and hepatocyte primary cultures. RKO and Hct116 cells were sensitive to both viruses, whereas LoVo cells were resistant. [35S]methionine labeling experiments and viral plaque assays showed that sensitive and resistant colorectal cancer cells supported viral protein and progeny production after infection with either virus. Colorectal cancer cells were pretreated with β-interferon and infected with vesicular stomatitis virus to evaluate the extent to which interferon signaling is downregulated in colorectal cancer cells. Although colorectal cancer cells retained some degree of interferon signaling, this signaling did not negatively impact the oncolytic effects of either virus in sensitive cells. Murine xenografts of RKO cells were effectively treated by intratumoral injections with M protein mutant virus, whereas LoVo xenografts were resistant to treatment with this virus. These results suggest that M protein mutant vesicular stomatitis virus is a good candidate oncolytic virus for the treatment of selected metastatic colorectal cancers.
PMCID: PMC3682425  PMID: 21886191
vesicular stomatitis virus; oncolytic virus; colorectal cancer; type I interferon; xenograft
22.  NLRC5-dependent activation of the inflammasome 
The nucleotide-binding domain (NBD) leucine rich repeat (LRR) containing proteins, NLRs, are intracellular sensors of PAMPs and DAMPs. A subgroup of NLRs can form inflammasome complexes, which facilitate the maturation of pro-caspase-1 to caspase-1, leading to IL-1β and IL-18 cleavage and secretion. NLRC5 is predominantly expressed in hematopoetic cells and has not been studied for inflammasome function. RNAi-mediated knockdown of NLRC5 nearly eliminated caspase-1, IL-1β and IL-18 processing in response to bacterial infection, PAMPs and DAMPs. This was confirmed in primary human monocytic cells. NLRC5 together with procaspase-1, pro-IL-1β and the inflammasome adaptor, ASC, reconstituted inflammasome activity which showed cooperativity with NLPR3. The range of pathogens that activate NLRC5 inflammasome overlaps with those that activate NLRP3. Furthermore, NLRC5 biochemically associates with NLRP3 in an NBD-dependent but LRR-inhibitory fashion. These results invoke a model where NLRC5 interacts with NLRP3 to cooperatively activate the inflammasome.
PMCID: PMC3669680  PMID: 21191067
23.  Conjugal Transfer of a Virulence Plasmid in the Opportunistic Intracellular Actinomycete Rhodococcus equi 
Journal of Bacteriology  2012;194(24):6790-6801.
Rhodococcus equi is a facultative intracellular, Gram-positive, soilborne actinomycete which can cause severe pyogranulomatous pneumonia with abscessation in young horses (foals) and in immunocompromised people, such as persons with AIDS. All strains of R. equi isolated from foals and approximately a third isolated from humans contain a large, ∼81-kb plasmid which is essential for the intramacrophage growth of the organism and for virulence in foals and murine in vivo model systems. We found that the entire virulence plasmid could be transferred from plasmid-containing strains of R. equi (donor) to plasmid-free R. equi strains (recipient) at a high frequency and that plasmid transmission reestablished the capacity for intracellular growth in macrophages. Plasmid transfer required living cells and cell-to-cell contact and was unaffected by the presence of DNase, factors pointing to conjugation as the major means of genetic transfer. Deletion of a putative relaxase-encoding gene, traA, located in the proposed conjugative region of the plasmid, abolished plasmid transfer. Reversion of the traA mutation restored plasmid transmissibility. Finally, plasmid transmission to other Rhodococcus species and some additional related organisms was demonstrated. This is the first study showing a virulence plasmid transfer in R. equi, and it establishes a mechanism by which the virulence plasmid can move among bacteria in the soil.
PMCID: PMC3510604  PMID: 23042997
24.  Adenosine Modification May Be Preferred for Reducing siRNA Immune Stimulation 
Nucleic Acid Therapeutics  2012;22(3):205-210.
The immune stimulation induced by short interfering RNAs (siRNAs) has been reported to be quieted or abrogated by methoxy or fluoro modifications of the 2′ position of the ribose sugar. However, variables such as the type of modification, nucleotide preference, and strand bias have not been systematically evaluated. Here, we report the results of a screen of several modified siRNAs via a human peripheral blood monocyte cytokine induction assay. Unlike corresponding modifications of guanosine, cytidine, or uridine, 2′-fluoro modification of adenosine significantly reduced cytokine induction while retaining siRNA knockdown activity. The results of this study suggest adenosine as an optimal target for modification.
PMCID: PMC4047996  PMID: 22519815
25.  Use of a KIT-specific monoclonal antibody to bypass imatinib resistance in gastrointestinal stromal tumors 
Oncoimmunology  2013;2(6):e24452.
Acquired resistance to imatinib is a significant problem for the clinical management of gastrointestinal stromal tumor (GIST) patients, and second-line small molecules have shown limited efficacy in this setting. We have recently demonstrated that a monoclonal antibody targeting KIT could potentially bypass imatinib resistance in preclinical models of GIST.
PMCID: PMC3716740  PMID: 23894705
CD117; gastrointestinal stromal tumor; imatinib; KIT; monoclonal antibody-based cancer therapy; receptor tyrosine kinase

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